swamirishi commented on code in PR #4006:
URL: https://github.com/apache/ozone/pull/4006#discussion_r1040187251
##########
hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/SCMCommonPlacementPolicy.java:
##########
@@ -426,4 +451,67 @@ public boolean isValidNode(DatanodeDetails datanodeDetails,
}
return false;
}
+
+ /**
+ * Given a set of replicas of a container which are
+ * neither over underreplicated nor overreplicated,
+ * return a set of replicas to copy to another node to fix misreplication.
+ * @param replicas
+ */
+ @Override
+ public Set<ContainerReplica> replicasToCopyToFixMisreplication(
+ Set<ContainerReplica> replicas) {
+ Map<Node, List<ContainerReplica>> placementGroupReplicaIdMap
+ = replicas.stream().collect(Collectors.groupingBy(replica ->
+ this.getPlacementGroup(replica.getDatanodeDetails())));
+
+ int totalNumberOfReplicas = replicas.size();
+ int requiredNumberOfPlacementGroups =
+ getRequiredRackCount(totalNumberOfReplicas);
+ int additionalNumberOfRacksRequired = Math.max(
+ requiredNumberOfPlacementGroups -
placementGroupReplicaIdMap.size(),
+ 0);
+ int replicasPerPlacementGroup =
+ getMaxReplicasPerRack(totalNumberOfReplicas);
+ Set<ContainerReplica> copyReplicaSet = Sets.newHashSet();
+
+ for (List<ContainerReplica> replicaList: placementGroupReplicaIdMap
+ .values()) {
+ if (replicaList.size() > replicasPerPlacementGroup) {
+ List<ContainerReplica> replicasToBeCopied = replicaList.stream()
+ .limit(replicaList.size() - replicasPerPlacementGroup)
+ .collect(Collectors.toList());
+ copyReplicaSet.addAll(replicasToBeCopied);
+ replicaList.removeAll(replicasToBeCopied);
+ }
+ }
+ if (additionalNumberOfRacksRequired > copyReplicaSet.size()) {
Review Comment:
This wouldn't work for the case say we have 5 replicas and 4 racks. Say
current placement has:
Rack 1: 2
Rack 2: 2
Rack 3: 1
In this case one of the replica from either Rack 1 or Rack 2 has to be
copied.
Max Replicas per rack is 2 in this case (5/4) + (5%4=1) = 2
So that is why I added another check for additionalNumberOfRacksRequired & I
am doing the same algorithm, but now comparing the rack with most replicas with
the rack with second highest number of replicas instead of directly removing
the number replicas.
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